"I'm the luckiest man on the planet," the Smashed actor tells PEOPLE. "It doesn't make sense to me. The way she looks at me ... she has that magical glow about her."

Paul – who is currently in London working on a film adaptation of Nick Hornby's novel A Long Way Down – recently revisited the spot in Paris where he popped the question.

"We got engaged over New Year's and I walked from the Eiffel Tower to St. Germain yesterday and I went to the stoop, the little step where I proposed to Lauren – and I took a picture of it and I sent it to her," he says.

"It's just this little courtyard outside of this hotel, and we were just dancing to Édith Piaf by ourselves on New Year's and then I begged her to marry me," he says of the proposal.